This invention relates to a method for the colorimetric determination of the percentage of protein in meat.
The rapid and accurate determination of the percentage of protein in meat is of particular importance to the meat processing industry to assure accurate batch-to-batch composition control whereby product uniformity and cost control may be optimized. For many years the most commonly utilized standard quantitative test for percentage of protein in meat and dairy products was generally considered to be Kjeldahl analysis, and particularly averaged duplicate Kjeldahl analyses.
Because of the length of time involved in carrying out an otherwise heretofore generally acceptable quantitive test such as a Kjeldahl analysis such tests are generally inadequate for in-plant quality and cost control. This is particularly so in large volume rapid meat processing plants utilizing computerized batch component/cost programming. In such plants it is necessary for on-line control purposes to have a rapid and accurate protein determination of all protein containing components of the batch as well as the final batch.
Thus, procedures are desired which combine a sufficient accuracy with simplicity in conducting the procedures. Direct colorimetric procedures are particularly desirable whereby involved analytical procedural steps and flammable or dangerous materials as in Kjeldahl analysis, can be dispensed with.
D. C. Udy, Nature Vol. 178, p 314 1956 and Cereal Chem. Vol. 33, p 190 describes methods for estimating protein in milk and wheat flour by dye binding procedures. In addition the Udy Dye Method adopted as official by the Assoc. Off. Anal. Chem. and U.S. Ashworth, Journal of Food Science, Vol. 36, p 509 (1971) describe methods wherein proteins in meat and egg products are determined colorimetrically by dye binding utilizing Acid Orange 12.
The foregoing conventional colorimetric methods for determination of the percentage of protein in meats exhibit disadvantages as to their accuracy and/or the time required for performance, and accordingly a relatively simple sufficiently accurate control test procedure has not heretofore been attained.
The foregoing dye binding methods depend upon the reaction between Acid Orange 12, a monoazo dye, Colour Index Constitution Number 15970, and the proteins of meat to form insoluble complexes. The complexes can be removed by filtration and the free dye concentration of the filtrate measured colorimetrically. A standard curve relating free dye concentration to mg of protein in the sample as determined by the Kjeldahl method can be prepared for various raw and processed meat products. In the above cited literature it has, for example, been reported that cooking, which effects the degree of denaturization of the protein, has little effect on the dye binding capacity, and therefore little effect upon the accuracy or variation in analysis performed in accordance with the therein described colorimetric methods. In addition, these conventional tests due to the therein described parameters of time and temperature, lead to inaccuracies that are unacceptable for present day computerized batch formulation of processed meat products.